class_docstr: Base class for Image, Audio and Video widgets.
  
  The `value` of this widget accepts a byte string.  The byte string is the
  raw data that you want the browser to display.
  
  If you pass `"url"` to the `"format"` trait, `value` will be interpreted
  as a URL as bytes encoded in UTF-8.
code: def _load_file_value(cls, filename):
      if getattr(filename, "read", None) is not None:
          return filename.read()
      else:
          with open(filename, "rb") as f:
              return f.read()
  
imports: import mimetypes
  from .widget_core import CoreWidget
  from .domwidget import DOMWidget
  from .valuewidget import ValueWidget
  from .widget import register
  from traitlets import Unicode, CUnicode, Bool
  from .trait_types import CByteMemoryView
label_desc: Use image node_id 4 for calling the _Media obj's underlying member method code with example usage: obj._load_file_value(cls, filename) and returns: filename, f